Partial Surface treatment apparatus

ABSTRACT

A partial surface treatment apparatus includes a first electrode member electrically connected to a treatment object having a circumferential groove at an outer circumferential surface thereof, a second electrode member having an annular-shaped inner circumferential surface facing the outer circumferential surface while keeping a distance therefrom, an elastic sealing member in an annular shape being sealable a clearance between the outer circumferential surface and the inner circumferential surface at portions on the outer circumferential surface above and below the circumferential groove, an attachment portion where the elastic sealing member is attached while keeping the distance from the outer circumferential surface, a pressure applying mechanism supplying a pressurized fluid into the elastic sealing member. to press-contact a radially inner circumferential end portion of the elastic sealing member against the outer circumferential surface and releasing a press-contact therebetween, and a supply passage through which an electrolyte is supplied to the circumferential groove.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority under 35 U.S.C. § 119 to Japanese Patent Application 2010-073794, filed on Mar. 26, 2010, and Japanese Patent Application 2010-287495, filed on Dec. 24, 2010, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

This disclosure generally relates to a partial surface treatment apparatus.

BACKGROUND DISCUSSION

Generally, a partial surface treatment apparatus is configured so that a clearance is formed between an outer circumferential surface of a workpiece (i.e. a treatment object) and an inner circumferential surface of a second electrode member. Furthermore, the known partial surface treatment apparatus, e.g. a surface treatment apparatus disclosed in JP2003-113496A, is configured so that an electrolyte is supplied to a portion of the clearance, which is sealed by an elastic sealing member provided at each end portion of a circumferential groove. Therefore, a surface treatment such as anodizing and the like is applicable to a portion of the outer circumferential surface of the workpiece having the circumferential groove. The surface treatment method and apparatus according to JP2003-113496A discloses that the clearance formed between the workpiece and the second electrode member is sealed in a manner where the elastic sealing members provided at the second electrode member are deformed by being compressed in a width direction thereof, so that an inner circumferential surface of each of the elastic sealing members press-fittingly contacts the outer circumferential surface of the workpiece.

Therefore, in a case where the workpiece is not set inside of the second electrode member so that the clearance formed between the outer circumferential surface of the workpiece and the inner circumferential surface of the second electrode member does not form a predetermined clearance along an entire circumference (in other words, in a case where the clearance formed between the outer circumferential surface of the workpiece and the inner circumferential surface of the second electrode member is not even along the entire circumference), a pressure force generated by the elastic sealing member relative to the outer circumferential surface of the workpiece may vary, which may result in reducing a sealing of the elastic sealing members relative to the outer circumferential surface of the workpiece. Furthermore, when a compression (i.e. a compressing amount) of each of the elastic sealing members fluctuates, a press-fittingly contacting position and press-fittingly contacting width (i.e. a length of a press-fittingly contacting portion of each of the elastic sealing members in a width direction of the circumferential groove) of each of the elastic sealing members relative to the outer circumferential surface of the workpiece also fluctuate. A detailed explanation about the drawback mentioned above will be described below with reference to FIG. 11, where an example of a known partial surface treatment apparatus is illustrated. As illustrated in FIG. 11, a center point P1 of a press-fittingly contacting position of an elastic sealing member 40 a, whose compression is small, is further away from a circumferential groove A1 relative to a center point P2 of a press-fittingly contacting position of an elastic sealing member 40 b, whose compression is greater than the compression of the elastic sealing member 40 a. Furthermore, a press-fittingly contacting width D1 of the elastic sealing member 40 a, whose compression is small, is narrower than a press-fittingly contacting width D2, whose compression is great. Therefore, when the compression of the elastic sealing member 40 fluctuates, an area where the electrolyte contacts an outer circumferential surface B of a workpiece A (which will be hereinafter referred to as an electrolyte contacting area) may not be easily set so as to correspond to a predetermined area. As a result, the surface treatment may be applied to the outer circumferential surface B of the workpiece A to a greater extent than the predetermined electrolyte contacting area. Accordingly, a treatment efficiency may easily be decreased.

A need thus exists to provide a partial surface treatment apparatus which is not susceptible to the drawback mentioned above.

SUMMARY

According to an aspect of this disclosure, a partial surface treatment apparatus includes a first electrode member electrically connected to a treatment object, which is made of a metal and which includes a circumferential groove at an outer circumferential surface of the treatment object, a second electrode member having an annular-shaped inner circumferential surface facing the outer circumferential surface and the circumferential groove while keeping a distance therefrom, an elastic sealing member made of a nonconductive material, formed in an annular shape and being sealable a clearance formed between the outer circumferential surface and the inner circumferential surface at portions on the outer circumferential surface above and below the circumferential groove in an axial direction of the partial surface treatment apparatus, an attachment portion at which the elastic sealing member is attached while keeping the distance relative to the outer circumferential surface along an entire circumference thereof, a pressure applying mechanism configured so as to supply a pressurized fluid into the elastic sealing member attached at the attachment portion in order to press-contact a radially inner circumferential end portion of the elastic sealing member against the outer circumferential surface along the entire circumference thereof and so as to release a press-contact of the radially inner circumferential end portion of the elastic sealing member against the outer circumferential surface, and a supply passage, through which an electrolyte is supplied to the circumferential groove, opening at the inner circumferential surface.

According to another aspect of this disclosure, a partial surface treatment apparatus, includes a first electrode member electrically connected to a treatment object, which is made of a metal and which includes a circumferential groove at an outer circumferential surface of the treatment object, a second electrode member having an annular-shaped inner circumferential surface acing the outer circumferential surface and the circumferential groove while keeping a distance therefrom, an elastic sealing member made of a nonconductive material, formed in an annular shape, being sealable a clearance formed between the outer circumferential surface and the inner circumferential surface at portions on the outer circumferential surface above and below the circumferential groove in an axial direction of the partial surface treatment apparatus, and including a recessed portion along an entire circumference thereof so as to open in a radially outward direction thereof and a displacement restricting portion so as to extend along an entire opening portion in a circumferential direction thereof in order to prevent a radially outer circumferential portion of the elastic sealing member defining the opening portion from being displaced towards the outer circumferential surface, an attachment portion at which the elastic sealing member is attached while keeping the distance relative to the outer circumferential surface along an entire circumference thereof, a pressure applying mechanism configured so as to supply a pressurized fluid into the elastic sealing member attached at the attachment portion in order to press-contact a radially inner circumferential end portion of the elastic sealing member against the outer circumferential surface along the entire circumference thereof and so as to release a press-contact of the radially inner circumferential end portion of the elastic sealing member against the outer circumferential surface, and a supply passage, through which an electrolyte is supplied to the circumferential groove, opening at the inner circumferential surface.

According to a further aspect of this disclosure, a partial surface treatment apparatus, includes a first electrode member electrically connected to a treatment object, which is made of a metal and which includes a circumferential groove at an outer circumferential surface of the treatment object, a second electrode member having an annular-shaped inner circumferential surface facing the outer circumferential surface and the circumferential groove while keeping a distance therefrom, an elastic sealing member made of a nonconductive material, formed in an annular shape, being sealable a clearance formed between the outer circumferential surface and the inner circumferential surface at portions on the outer circumferential surface above and below the circumferential groove in an axial direction of the partial surface treatment apparatus and including a contact surface, at which the elastic sealing member is contactable with the outer circumferential surface, and a corner portion, which is positioned so as to be closer to the circumferential groove and which guides a side surface to extend in a direction orthogonal to the outer circumferential surface, so as to extend along the entire circumference of the elastic sealing member in an annular shape, an attachment portion at which the elastic sealing member is attached while keeping the distance relative to the outer circumferential surface along an entire circumference thereof, a pressure applying mechanism configured so as to supply a pressurized fluid into the elastic sealing member attached at the attachment portion in order to press-contact a radially inner circumferential end portion of the elastic sealing member against the outer circumferential surface along the entire circumference thereof and so as to release a press-contact of the radially inner circumferential end portion of the elastic sealing member against the outer circumferential surface, and a supply passage, through which an electrolyte is supplied to the circumferential groove, opening at the inner circumferential surface.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and additional features and characteristics of this disclosure will become more apparent from the following detailed description considered with the reference to the accompanying drawings, wherein:

FIG. 1 is a diagram schematically illustrating a partial surface treatment apparatus according to the embodiments;

FIG. 2 is a plane view illustrating a second electrode member taken along line II-II in FIG. 1;

FIG. 3 is a cross-sectional diagram illustrating an electrolyte supplying nozzle portion of the second electrode member;

FIG. 4 is a side view illustrating an inner circumferential portion of the electrolyte supplying nozzle of the second electrode member;

FIG. 5 is a cross-sectional diagram illustrating a state where an elastic sealing member of the second electrode member is away from an outer circumferential surface of a piston;

FIG. 6 is a cross-sectional diagram illustrating a state where the elastic sealing member of the second electrode member press-fittingly contacts the outer circumferential surface of the piston;

FIG. 7 is an enlarged cross-sectional diagram of the elastic sealing member;

FIG. 8A is a cross-sectional diagram illustrating an inner circumferential surface of a second electrode member of a partial surface treatment apparatus according to a second embodiment in a case where the elastic sealing member is away from an outer circumferential surface of a piston;

FIG. 8B is a cross-sectional diagram illustrating the inner circumferential surface of the second electrode member of the partial surface treatment apparatus according to the second embodiment in a case where the elastic sealing member press-fittingly contacts the outer circumferential surface of the piston;

FIGS. 9A and 9B are diagrams schematically illustrating a elastic sealing member according to a third embodiment;

FIG. 10A is a diagram illustrating a state of a partial surface treatment apparatus before a compressed air is supplied to a recessed portion of the elastic sealing member according to the third embodiment;

FIG. 10B is a diagram illustrating a state of the partial surface treatment apparatus after the compressed air is supplied to the recessed portion of the elastic sealing member according to the third embodiment; and

FIG. 11 is a cross-sectional diagram of a known partial surface treatment apparatus, where an elastic sealing member is in a sealing state.

DETAILED DESCRIPTION

Embodiments of a partial surface treatment apparatus will be described below with reference to the attached drawings. Additionally, portions having identical reference numerals as in FIG. 11 of the prior art indicate the identical or similar (corresponding) components.

First Embodiment

The partial surface treatment apparatus according to the first embodiment is configured so as to execute a surface treatment to a workpiece (a treatment object) made of a metal. In this embodiment, a piston ring groove A1 of a piston A made of an aluminum alloy corresponds to the metal made treatment object. Furthermore, in this embodiment, anodizing treatment is adapted as an example of the surface treatment. In other words, in this embodiment, the partial surface treatment apparatus is described below as an anodizing treatment apparatus. Illustrated in FIGS. 1 to 6 are the anodizing treatment apparatus, which executes the anodizing treatment to the piston ring groove A1 of the piston A made of the aluminum alloy. Additionally, “the piston ring groove A1 of the aluminum alloy made piston A”, “the anodizing treatment” and “the anodizing treatment apparatus” are examples, therefore the partial surface treatment apparatus is adaptable to other surface treatments.

More specifically, in this embodiment, it is supposed that the anodizing treatment is applied to an outer circumferential surface B including the piston ring groove A1 (i.e. a compression ring groove) positioned closer to a top portion of the piston A out of three piston ring grooves A1, A2 and A3. In this embodiment, the outer circumferential surface B including the piston ring groove A1 is hereinafter referred to as a piston outer circumferential surface. The piston ring grooves A1, A2 and A3 are formed on the piston A so that the piston ring groove A1 is positioned closer to the top portion of the piston A, the piston ring groove A3 is positioned at a skirt portion of the piston A and the piston ring groove A2 is positioned between the piston ring grooves A1 and A3. The piston ring groove A1 corresponds to a circumferential groove formed on the piston outer circumferential surface B.

The anodizing treatment apparatus includes an electrolytic cell 1, an electrolyte supplying portion 2, an oxidation treatment portion 3 and an electrifying portion 4.

As illustrated in FIGS. 1 and 2, the electrolyte cell 1, which is made of a chloroethene or a stainless steel SUS316, is formed in a container having an opening portion at an upper end portion thereof. The electrolyte cell 1 receives an electrolyte, which flows through the oxidation treatment portion 3 in order to collect the electrolyte. Furthermore, the electrolyte cell 1 includes a reflux passage 5 for flowing back the electrolyte to the electrolyte supplying portion 2.

The electrolyte supplying portion 2 includes a cooling tank 6 for cooling down a temperature of the electrolyte, which is flown back thereto from the electrolyte cell 1, a supply passage 7 through which the electrolyte in the cooling tank 6 is supplied to the oxidation treatment portion 3, a supply pump 8 provided at the supply passage 7, and a supply control portion 9, which controls an actuation of the supply pump 8 in order to supply the electrolyte to the oxidation treatment portion 3 at a predetermined timing.

The cooling tank 6 includes a cooling device 10, which cools down the temperature of the collected electrolyte, and a cooling control portion 12, which is configured so as to control an actuation of the cooling device 10 on the basis of a detection information of the electrolyte temperature obtained by a temperature sensor 11 so that the electrolyte is cooled down to a predetermined temperature.

The electrifying portion 4 electrifies the oxidation treatment portion 3. The electrifying portion 4 may be configured so as to include a current control means, so that the electrifying portion 4 may adjust a current density. Additionally, a known current control means configured with an ampere meter, a voltage indicator, a rectifier and the like may be used as the current control means.

The oxidation treatment portion 3 includes a first electrode portion 13 (anode) and a second electrode portion 14 (cathode). The first electrode portion 13 includes a first electrode member 15, which is made of a metal such as a copper or the stainless steel SUS316 having electric conductivity, and a lifting device 16, which is configured so as to lift up and lift down the first electrode member 15 relative to the second electrode portion 14. The first electrode member 15 also serves as a retaining member for supporting and retaining the piston A. Furthermore, the first electrode member 15 is electrically connected to an anode terminal 4 a of the electrifying portion 4.

The retaining member 15 (i.e. the first electrode member 15) includes an engagement pawl at a lower end portion thereof, so that the retaining member 15 is engageable with and disengageable from an inner circumferential surface of the piston A. The retaining member 15 retains the piston A while being electrically connected to the retaining member 15 in a manner where the engagement pawl engages with the inner circumferential surface of the piston A, so that a shaft center of the piston A extends in a vertical direction.

As illustrated in FIG. 2, the second electrode portion 14 is formed so that an outer shape thereof forms a round shape in a plane view. Furthermore, the second electrode portion 14 includes a piston insertion bore 25, which extends in a concentric manner and which is formed in a round shape in a plane view. Accordingly, the piston A is inserted into the piston insertion bore 25 so that the shaft center of the piston A extends in an up-and-down direction along the piston insertion bore 25.

As illustrated in FIG. 1, the second electrode portion 14 includes a second electrode member 17, a first fixing plate 18, a second fixing plate 19 and a supporting board 20. The second electrode member 17 is made of a metal such as the copper or the stainless steel SUS316 having the electric conductivity. On the other hand, each of the first and second fixing plates 18 and 19 is made of a nonconductive material (insulator) such as a polyvinyl chloride resin and the like. Furthermore, the first and second fixing plates 18 and 19 are arranged so as to sandwich the second electrode member 17, more specifically, the first fixing plate 18 is arranged at an upper portion of the second electrode member 17 and the second fixing plate 18 is arranged at a lower portion of the second electrode member 17. The first fixing plate 18 and the second fixing plate 19 are connected to each other by means of a bolt (bolts) and the like. Similarly, the second fixing plate 19 and the supporting board 20 are connected to each other by means of a bolt (bolts) and the like.

The second electrode member 17 is provided between an upwardly-opened recessed surface portion 21 and a downwardly-opened recessed surface portion 22 so as to be fitted into a space formed therebetween. Furthermore, the second electrode member 17 is connected to each of the upwardly-opened recessed surface portion 21 and the downwardly-opened recessed surface portion 22 by means of a bolt (bolts) and the like. The upwardly-opened recessed surface portion 21 is formed at an outer circumferential lower surface of the first fixing plate 18 in an annular shape so as to recess upwardly. On the other hand, the downwardly-opened recessed surface portion 22 is formed at an outer circumferential upper surface of the second fixing plate 19 in an annular shape so as to recess downwardly.

As illustrated in FIG. 1, the second electrode member 17 is configured with a first electrode plate 23 and a second electrode plate 24, which are connected to each other by means of a bolt (bolts) and the like in a state where the first electrode plate 23 is arranged upon the second electrode plate 24. The second electrode member 17 is electrically connected to a cathode terminal 4 b of the electrifying portion 4.

The first electrode plate 23 includes an outer circumferential portion 26 and a first thin plate portion 27, which is formed to be thinner than the outer circumferential portion 26. Similarly, the second electrode plate 24 includes an outer circumferential portion 26 and a second thin plate portion 28, which is formed to be thinner than the outer circumferential portion 26. As illustrated in FIGS. 3 to 6, each of a first flange plate portion 29 and a second flange plate portion 30 is formed in an annular shape so as to extend towards the piston insertion bore 25 along a radially inner circumferential portion of each of the first and second thin plate portions 27 and 28. A space formed between radially inner circumferential surfaces 31 (which will be hereinafter referred to as electrode inner circumferential surfaces 31) of respective the first flange plate portion 29 and the second flange plate portion 30 is in communication with the piston insertion bore 25. Therefore, the electrode inner circumferential surface of each of the first and second flange plate portions 29 and 30 is formed as an annular-shaped inner circumferential surface facing the piston outer circumferential surface B while being spaced away from the piston outer circumferential surface B along the entire circumference thereof.

The second fixing plate 19 includes a round-shaped recessed surface portion 32 and a round-shaped protruding surface portion 35. The round-shaped recessed surface portion 32 is formed so that a diameter thereof corresponds to the piston insertion bore 25 in a concentric manner. On the other hand, the round-shaped protruding surface portion 35 allows a bottom surface of the piston A to contact thereon in order to support the piston A in a state where the axial center of the piston A extends in the up-and-down direction. The second fixing plate 19 includes a connecting fluid passage 33, which also extends through the ,supporting board 20 and which is connected to a supply passage 7 of the electrolyte, and a discharge bore 34, which also extends through the supporting board 20 and through which the electrolyte accumulated within the round-shaped recessed surface portion 32 is naturally discharged (due to the gravity) to the electrolyte cell 1.

Accordingly, as illustrated in FIG. 1, the piston A, which is retained by the first electrode member 15 (i.e. the retaining member) in the state where the piston A is electrically connected to the first electrode member 15 while the axial center of the piston A extends in the vertical direction, is inserted into the piston insertion bore 25 and the bottom surface of the piston A is placed on the round-shaped protruding surface portion 35. Accordingly, as illustrated in FIG. 3, the piston A is arranged at a position so that the piston outer circumferential surface B is being away from an entire electrode inner circumferential surface 31 (an inner circumferential surface) so as to form a constant clearance C therebetween in a concentric manner.

As illustrated in FIGS. 2 to 4, plural electrolyte supply nozzles 36 are arranged in a circumferential direction between the first thin plate portion 27 and the first flange portion 29 of the first electrode plate 23 on the one hand and the second thin plate portion 28 and the second flange portion 30 of the second electrode plate 24 on the other hand while keeping a predetermined distance between the neighboring electrolyte supply nozzles 36 in the circumferential direction.

Each electrolyte supply nozzle 36 is arranged so that the electrolyte is supplied between the piston outer circumferential surface B and the electrode inner circumferential surfaces 31 in a direction inclined relative to a tangential line of, the electrode inner circumferential surfaces 31.

As illustrated in FIGS. 3 and 4, each electrolyte supply nozzle 36 is connected to the connecting fluid passage 33. Furthermore, each electrolyte supply nozzle 36 includes a supply passage 37 through which the electrolyte is supplied between the piston outer circumferential surface B and the electrode inner circumferential surfaces 31. The supply passage 37 of each electrolyte supply nozzle 36 opens at the electrode inner circumferential surfaces 31.

As illustrated in FIGS. 1 and 4, a clearance defined by the first thin plate portion 27 and the first flange portion 29 on the one hand and the second thin plate portion 28 and the second flange portion 30 on the other hand between the neighboring electrolyte supply nozzles 36 serves as a discharge passage 38.

As illustrated in FIG. 2, a through bore 39, which extends through the second thin plate portion 28, the second fixing plate 19 and the supporting board 20, is formed between the neighboring electrolyte supply nozzles 36 in the circumferential direction. The electrolyte within the discharge passage 38 is naturally discharged towards the electrolyte cell 1 through the through bores 39 by gravity.

As illustrated in FIGS. 1, 3, 4, 5 and 6, a pair of annular-shaped nonconductive elastic sealing members 40 are provided at the respective electrode inner circumferential surfaces 31 of the second electrode member 17. The attachment portions 41 (i.e. a first attachment portion 41 a and a second attachment portion 41 b) are formed at inner circumferential surfaces of the first and second fixing plates 18 and 19, respectively, in order to attach and retain the corresponding elastic sealing members 40 while keeping a clearance relative to the entire piston outer circumferential surface B.

Each elastic sealing member 40 is made of a nonconductive material (an insulator) such as rubber and the like and is formed in the annular shape. The elastic sealing members 40 are configured so as to seal a clearance C formed between the piston outer circumferential surface B and the electrode inner circumferential surfaces 31 at upper and lower positions relative to the piston ring groove A1 (i.e. the circumferential groove), respectively.

As illustrated also in FIG. 7, each elastic sealing member 40 is formed in a transversely U-shape in cross-section so as to include a recessed portion 42 that opens in a radially outward direction (i.e. a direction opposite to the piston insertion bore 25), a radially inner circumferential end portion 44, which is contactable with the piston outer circumferential surface B, and side portions 43 extending from respective end portions of the radially inner circumferential end portion in a radial direction.

The attachment portion 41 includes the first attachment portion 41 a and the second attachment portion 41 b. The first attachment portion 41 a is formed so that the elastic sealing member 40 is fittingly attached between an upper surface of the first flange portion 29 of the first electrode plate 23 and a lower surface of the first fixing plate 18, so that the upper side portion 43 fittingly contacts the lower surface of the fixing plate 18 and the lower side portion 43 fittingly contacts the upper surface of the flange portion 29. Similarly, the second attachment portion 41 b is formed so that the elastic sealing member 40 is fittingly attached between a lower surface of the second flange portion 30 of the second electrode plate 24 and an upper surface of the second fixing plate 19, so that the upper side portion 43 fittingly contacts the lower surface of the second flange portion 30 and the lower side portion 43 fittingly contacts the upper surface of the second fixing plate 19. Furthermore, each of the first and second attachment portion 41 a and 41 b is formed so that the inner circumferential end portion 44 of each of the elastic sealing members 40 does not protrude towards the piston outer circumferential surface B relative to the electrode inner circumferential surfaces 31 when the partial surface treatment apparatus is not actuated.

As illustrated in FIGS. 3 and 7, a displacement restricting portion 45 for restricting a displacement of an opening portion of each elastic sealing member 40 towards the piston outer circumferential surface B is formed at an end portion defining the opening portion of the recessed portion 42 so as to extend along the entire elastic sealing member 40 in the circumferential direction.

More specifically, the displacement restricting portion 45, which also serves as an engagement flange 46, is integrally formed at an end portion of each of the upper and lower side portions 43 of each of the elastic sealing members 40. The engagement flange 46 of the elastic sealing members 40 are engaged with the first and second attachment portion 41 a and 41 b, respectively. Accordingly, the end portions of the upper and lower side portions 43 of each of the elastic sealing members 40 are prevented from being displaced towards the piston outer circumferential surface B.

An engagement groove 47 in an annular shape is formed at the upper surface of the first flange portion 29 of the first electrode plate 23. Furthermore, an engagement groove 48 in an annular shape is formed at the lower surface of the first attachment portion 41 a. Accordingly, the engagement flanges 46 (displacement restricting portions 45) of the elastic sealing member 40 are engaged with the engagement groove 47 and the engagement groove 48, respectively. Similarly, an engagement groove 49 is formed at the lower surface of the second flange portion 30 of the second electrode plate 24. Furthermore, an engagement groove 50 is formed at the upper surface of the second attachment portion 41 b. Accordingly, the displacement restricting portions 46 (the engagement flanges) of the elastic sealing member 40 are engaged with the engagement groove 49 and the engagement groove 50, respectively.

As illustrated in FIGS. 1, 5 and 6, the partial surface treatment apparatus includes a pressure applying mechanism 51. The pressure applying mechanism 51 is configured so as to simultaneously supply compressed air, which serves as a pressurized fluid, into the recessed portions 42 of the elastic sealing members 40, which are attached at the first and second attachment portions 41 a and 41 b, respectively, so that the elastic sealing members 40 (the radially inner circumferential end portions 44) press-fittingly contact the piston outer circumferential surface B along the entire circumference thereof, and so as to release the press-contact of the elastic sealing members 40 against the piston outer circumferential surface B.

The pressure supplying mechanism 51 includes an air supply/discharge apparatus 52, an air supply/discharge control portion 53, an air supply/discharge passage 54 and a pipe (tube) connector 56. The air supply/discharge apparatus 52 is configured so as to supply and discharge the compressed air to and from the recessed portions 42 of the respective elastic sealing members 40. The air supply/discharge control portion 53 is configured so as to control the air supply/discharge apparatus 52. The air supply/discharge passage 54 is configured so as to be in communication with each of the recessed portions 42 of the respective elastic sealing members 40, which are attached at the respective first and second attachment portions 41 a and 41 b. The pipe connector 56 connects an air supply/discharge pipe (tube) 55 of the air supply/discharge apparatus 52 with the air supply/discharge passage 54.

The air supply/discharge passage 54 is provided at three portions of the second electrode portion 14 in a circumferential direction thereof. Furthermore, each air supply/discharge passage 54 is connected to the air supply/discharge pipe 55, so that the compressed air is supplied to and discharged from the recessed portions 42 of the respective elastic sealing members 40 from three portions thereof in the circumferential direction.

A detailed explanation about the air supply/discharge mechanism 51 will be given below. As illustrated in FIG. 5, after the piston A is inserted into the piston insertion bore 25 so that the piston A contacts and is placed on the round-shaped recessed surface portion 35, the air supply/discharge control portion 53 actuates the air supply/discharge apparatus 52 to supply the compressed air to each of the recessed portions 42 of the respective elastic sealing members 40 through the air supply/discharge passages 54.

The upper and lower side portions 42 of each of the elastic sealing members 40 are elastically stretched towards the piston outer circumferential surface B in response to the compressed air supplied to each of the recessed portions 42 of the respective elastic sealing members 40, so that the inner circumferential end portion of each of the elastic sealing members 40 elastically spreads (protrudes) towards the piston outer circumferential surface B. Accordingly, as illustrated in FIG. 6, the radially inner circumferential end portions 44 of the respective elastic sealing members 40 press-fittingly contact the piston outer circumferential surface B.

Accordingly, the upper and lower side portions 43 of the elastic sealing member 40 positioned above the other elastic sealing member 40 are pressed against the first fixing plate 19 and the first flange portion 29, respectively in response to the compressed air supplied to the corresponding recessed portion 42. Similarly, the upper and lower side portions 43 of the other elastic sealing member 40 are pressed against the second flange portion 30 and the second fixing plate 20, respectively, in response to the compressed air supplied to the corresponding recessed portion 42. As a result, a posture of the elastic sealing members 40 is stabilized and furthermore, the compressed air is avoided from leaking to the piston outer circumferential surface B.

Accordingly, because the radially inner circumferential end portions 44 of the respective elastic sealing members 40 press-fittingly contact the piston outer circumferential surface B, the clearance C defined by the piston outer circumferential surface B and the electrode inner circumferential surfaces 31 is sealed by the elastic sealing members 40 at the positions above and below the piston ring groove A1. Then, the anodizing treatment is applied to the piston ring groove A1 (i.e. the circumferential groove) while circulating the electrolyte in a manner where the electrolyte is discharged from the discharge passage 38 through the supply passage 37 and a clearance formed between the electrode inner circumferential surfaces 31 and the piston ring groove A1.

After the anodizing treatment to the piston ring groove A1 is completed, the air supply/discharge control portion 53 actuates the air supply/discharge apparatus 52 so that the compressed air is forcibly discharged from the recessed portions 42 of the respective elastic sealing members 40 through the air supply/discharge passages 54 and the air supply/discharge pipe 55, in other words, so that the press-fit contact of the elastic sealing members 40 against the piston outer circumferential surface B is released.

The upper and lower side portions 43 and the radially inner circumferential end portion 44 of each of the elastic sealing members 40 are elastically deformed so as to form (return to) initial shapes in response to the discharge of the compressed air from the corresponding recessed portion 42. Accordingly, as illustrated in FIG. 5, the radially inner circumferential end portions 44 of the respective elastic sealing members 40, which press-fittingly contact the piston outer circumferential surface B, are displaced away from the electrode inner circumferential surfaces 31, so that the radially inner circumferential end portions 44 of the respective elastic sealing members 40 are elastically returned so as to be positioned radially outwardly of the electrode inner circumferential surfaces 31. Furthermore, because the compressed air is forcibly discharged, the radially inner circumferential end portions 44 of the respective elastic sealing members 40 are surely and properly retracted so as to be positioned radially outwardly of the electrode inner circumferential surfaces 31 (so as not to be protrude towards the piston outer circumferential surface B from the electrode inner circumferential surfaces 31).

Second Embodiment

A second embodiment of the partial surface treatment apparatus will be described below. Illustrated in FIGS. 8A and 8B are a major portion of the partial surface treatment apparatus according to the second embodiment. In the second embodiment, the elastic sealing members 40, which are attached at the anodizing treatment apparatus, are modified. As illustrated in FIGS. 8A and 8B, each of the elastic sealing members 40 includes a contact surface 57, at which each of the elastic sealing members 40 are allowed to contact the piston outer circumferential surface B and which are formed along the entire circumferential direction so as to from an annular shape, and side surfaces 58 extending from respective end portions of the contact surface 57 via corresponding corner portions 59 along the entire circumferential direction so a to from an annular shape. Accordingly, because each of the elastic sealing members 40 includes the corner portions 59, the side surfaces 58 extend in a direction orthogonal to the piston outer circumferential surface B.

Accordingly, as illustrated in FIG. 8B, because the elastic sealing members 40 configured as described above are attached at the respective attachment portions 41 (i.e. the first attachment portion 41 a and the second attachment portion 41 b), a border of an electrolyte contact area may be set along the corner portions 59, which are formed in the annular shape along the respective inner circumferential end portions 44. Accordingly, the electrolyte contact area may be easily set to any desired area. Other configurations of the partial surface treatment apparatus according to the second embodiment are similar to the partial surface treatment apparatus according to the first embodiment.

Third Embodiment

A third embodiment of the partial surface treatment apparatus will be described below. In the third embodiment, the elastic sealing members 40, which are attached at the anodizing treatment apparatus according to the first embodiment, are modified. Other configurations of the partial surface treatment apparatus according to the third embodiment are similar to the partial surface treatment apparatus according to the first embodiment. Therefore, the differences between the first embodiment and the third embodiment will be mainly described below.

Illustrated in FIGS. 9A and 9B are the elastic sealing member 40 adapted to the partial surface treatment apparatus according to the third embodiment. More specifically, illustrated in FIG. 9A is a perspective view of the elastic sealing member 40. In order to facilitate understanding, a portion of the elastic sealing member 40 is illustrated in cross-section. On the other hand, illustrated in FIG. 9B is an enlarged diagram of a cross-sectional surface of the elastic sealing member 40. As illustrated in FIG. 9A, the elastic sealing member 40 is formed in an annular shape. Furthermore, the elastic sealing member 40 includes the recessed portion 42, which opens in the radially outward direction, so as to extend along the entire circumference of the elastic sealing member 40.

In order to facilitate understanding, the piston outer circumferential surface B, the attachment portion 41 and the second electrode member 17 are illustrated by a chain double-dashed line in FIG. 9B. As illustrated in FIG. 9B, a contact surface Z of the elastic sealing member 40, at which the elastic sealing member 40 is allowed to contact the piston outer circumferential surface B, is formed as a surface extending in parallel to an axial direction of the elastic sealing member 40. The contact surface Z of the elastic sealing member 40 is a radially inner circumferential surface of the elastic sealing member 40, which is formed in the annular shape, in other words, the contact surface Z faces the piston outer circumferential surface B. The axial direction of the elastic sealing member 40 refers to a direction extending through the annular shape of the elastic sealing member 40 at a center the annular shape. Accordingly, the contact surface Z of the elastic sealing member 40 is configured as the surface parallel to the axial direction. Therefore, a cylinder extending along the axial direction if formed (defined) by the radially inner circumferential surface of the elastic sealing member 40.

The elastic sealing member 40 is inserted into a groove portion 71, which is formed between the attachment portion 41 and the second electrode member 17. Illustrated in FIG. 9B is the elastic sealing member 40 before being inserted into the groove portion 71. As illustrated in FIG. 9B, the elastic sealing member 40 is formed so that a width 81 c thereof in the axial direction between radially outer circumferential edge portions 81 is greater than an opening width 71 a of the groove portion 71. The radially outer circumferential edge portion 81 refers to an edge portions of the elastic sealing member 40 positioned at a radially outer circumferential portion. In the third embodiment illustrated in FIG. 9B, a first radially outer circumferential edge portion 81 a and a second radially outer circumferential edge portion 81 b correspond to the radially outer circumferential edge portions 81. Accordingly, the width 81 c in the axial direction between the radially outer circumferential edge portions 81 corresponds to a distance between the first and second radially outer circumferential edge portions 81 a and 81 b. The elastic sealing member 40 is formed so that the width 81 c in the axial direction between the radially outer circumferential edge surfaces 81 is greater than the opening width 71 a of the groove portion 71, which is defined by the attachment portion 41 and the second electrode member 17.

Furthermore, the elastic sealing member 40 is formed so that a width 82 c in the axial direction between radially inner circumferential edge portions of the elastic sealing member 40 before being inserted into the groove portion 71 is set to be shorter (narrower) than the opening width 71 a of the groove portion 71. In this embodiment, edge portions of the radially inner circumferential surface correspond to the radially inner circumferential edge portions 82 of the elastic sealing member 40. In this embodiment illustrated in FIG. 9B, a first radially inner circumferential edge portion 82 a and a second radially inner circumferential edge portion 82 b correspond to the radially inner circumferential edge portions 82. Accordingly, the width 82 c in the axial direction between the radially inner circumferential edge portions 82 corresponds to a distance between the first and second radially inner circumferential edge portions 82 a and 82 b. Accordingly, the elastic sealing member 40 is formed so that the width 82 c in the axial direction between the radially inner circumferential edge portions 82 is shorter than the opening width 71 a of the groove portion 71, which is defined by the attachment portion 41 and the second electrode member 17.

More specifically, in this embodiment, each of upper and lower side wall portions 43 defining the recessed portion 42 may be formed to incline by 3.5 degree to 10 degree relative to an orthogonal plane orthogonal to the contact surface Z of the elastic sealing member 40. Furthermore, a thickness of each of the upper and lower side wall portions 43 may be formed in a range between 1.5 mm to 2.5 mm (including 1.5 mm and 2.5 mm). Accordingly, because the elastic sealing member 40 is configured as described above, sealing (contact) of the elastic sealing member 40 relative to the attachment portion 41 and the second electrode member 17 may be increased. Additionally, either one of or both of the upper and lower side wall portions 43 may be formed so as to incline less than 3.5 degrees relative to a radial direction of the elastic sealing member 40, or so as to incline greater than 10 degrees relative to the radial direction of the elastic sealing member 40. Still further, the thickness of either one of or both of the upper and lower side wall portions 43 may be formed to be thinner than 1.5 mm, or so as to be thicker than 2.5 mm.

A case where the compressed air is supplied to the recessed portion 42 of the elastic sealing member 40 according to the third embodiment will be described below. Illustrated in FIG. 10A is a state of the elastic sealing members 40 before the compressed air is supplied to each of the recessed portions 42 of the respective elastic sealing members 40. On the other hand, illustrated in FIG. 10B is a state of the elastic sealing member 40 after the compressed air (a pressurized fluid) is supplied to each of the recessed portions 42 of the respective elastic sealing members 40. As illustrated in FIG. 10A, when the compressed air is supplied to each of the recessed portions 42 of the respective elastic sealing members 40, both of the radially outer circumferential edge portions 81 and the radially inner circumferential edge portions 82 of each elastic sealing member 40 are displaced towards the center of the elastic sealing member 40 in the radial direction in response to the supply of the compressed air to the corresponding recessed portion 42. Accordingly, the radially inner circumferential end portions 44 of the respective elastic sealing members 40 are displaced towards the piston outer circumferential surface B, so that the radially inner circumferential end portions 44 of the respective elastic sealing members 40 press-fittingly contact the piston outer circumferential surface B as illustrated in FIG. 10B. Accordingly, the partial surface treatment apparatus according to the third embodiment may appropriately and properly seal the clearance C formed between the piston outer circumferential surface B and the entire electrode inner circumferential surface 31.

Furthermore, the upper and lower side wall portions 43 of each of the elastic sealing members 40 also slide (move) towards the piston outer circumferential surface B in response to the supply of the compressed air to the corresponding recessed portion 42. Accordingly, the upper and lower side wall portions 43 of the elastic sealing member 40, which is arranged above the other one of the elastic sealing member 40, are pressed against the corresponding attachment portion 41 (the first attachment portion 41 a) and the second electrode member 17, respectively. On the other hand, the upper and the lower side wall portions 43 of the other elastic sealing member 40, are pressed against the second electrode member 17 and the corresponding attachment portion 41 (the second attachment portion 41 b). As a result, the sealing (the contact) between the elastic sealing members 40 on the one hand and the attachment portions 41 and the second electrode member 17 on the other hand is increased. Therefore, the electrolyte used for the anodizing treatment may be avoided from leaking to the piston outer circumferential surface B.

Accordingly, because the radially inner circumferential end portions 44 of the respective elastic sealing members 40 press-fittingly contact the piston outer circumferential surface B, the clearance C between the piston outer circumferential surface B and the electrode inner circumferential surface 31 is sealed at the positions above and below the piston ring groove A1 (the circumferential groove). While the above-mentioned state is established, the electrolyte used for the anodizing treatment is discharged and circulated through the supply passage 37 and the clearance formed between the electrode inner circumferential surface 31 and the piston ring groove A1. Accordingly, the anodizing treatment is applied to the piston ring groove A1.

The partial surface treatment apparatus according to the third embodiment may be modified as follows.

Firstly, the partial surface treatment apparatus according to the third embodiment may be modified so that each elastic sealing member 40 is formed so as to be protrudable in a radially inward direction relative to a groove portion 71, which is formed in an annular-shape having an opening in the radially inward direction by the corresponding attachment portion 41 and the second electrode portion 17. Accordingly, the clearance formed between the piston outer circumferential surface B and the electrode inner circumferential surface 31 may be narrowed. As a result, a large amount of the electrolyte may be provided into the narrow clearance formed between the piston outer circumferential surface B and the electrode inner circumferential surface 31, which may further result in increasing a speed of surface treatment (shortening time necessary for the surface treatment).

Secondly, the partial surface treatment apparatus according to the third embodiment may be modified so that each of the elastic sealing members 40 includes the side wall portions 43 defining the recessed portion 42 so that the thickness of each of the side wall portions 43 is formed to be thinner than the opening width of the recessed portion in the axial direction. Accordingly, the side wall portions 43 of each of the elastic sealing members 40 become more easily deformable, therefore, the side wall portions 43 of each of the elastic sealing members 40 more easily press-contact a wall surface of the groove portion 71 by the compressed air (the pressurized fluid). As a result, the sealing (the contact) of the elastic sealing members 40 against the wall surface of the groove portion 71 may be increased. Furthermore, in a case where a pressure applied to the elastic sealing members 40 is eased (removed), each of the elastic sealing members 40 is enlarged in the diametrical direction in the radially outward direction while a pressing force of the wall portions 43 is eased. Therefore, a force applied to the elastic sealing members 40 while being enlarged in the diametrical direction may be eased. Accordingly, durability of the elastic sealing members 40 may be enhanced.

Thirdly, the partial surface treatment apparatus according to the third embodiment may be modified so that the recessed portion 42 of each of the elastic sealing members 40 includes a wall surface Y (a wall portion serving as a bottom portion (bottom surface) of the recessed portion 42) so as to be positioned closer to the radially inner circumferential edge portions. Furthermore, the wall surface Y of each of the elastic sealing members 40 may be formed so as to be positioned closer to the radially inner circumferential edge portions relative to an intermediate position between the radially outer circumferential edge portions and the radially inner circumferential edge portions of each of the elastic sealing members 40. Accordingly, each of the elastic sealing members 40 may be easily elastically deformable in an inner diameter reducing direction, so that the elastic sealing members 40 may more easily press-fittingly contact the piston outer circumferential surface B. As a result, the sealing (the contact) of the elastic sealing members 40 relative to the piston outer circumferential surface B may be enhanced.

Fourthly, the partial surface treatment apparatus according to the third embodiment may be modified so that the recessed portion 42 of each of the elastic sealing members 40 includes the wall surface Y (the wall portion) so as to be positioned closer to the radially inner circumferential edge portions. Furthermore, the wall surface Y may be formed as a surface parallel to the axial direction of each elastic sealing member 40, so that the wall surface Y extends along a contact surface of the corresponding elastic sealing member 40 at which elastic sealing member 40 contacts the piston outer circumferential surface B of the piston A. Accordingly, the wall surface Y serving as the bottom portion of the recessed portion 43 is formed as a surface parallel to the contact surface Z of the corresponding elastic sealing member 40 at which the elastic sealing member 40 contacts the outer circumferential surface B of the piston A. Therefore, the contact surface Z of each of the elastic sealing members 40 may evenly pressed against the piston outer circumferential surface B by the compressed air (the pressurized fluid). As a result, the sealing (the contact) of the elastic sealing members 40 against the piston outer circumferential surface B may be enhanced.

Fifthly, the partial surface treatment apparatus according to the third embodiment may be modified so that the elastic sealing members 40 are slidably displaced in the radially inward direction while pressing the wall surface of the groove portion 71 in the case where the elastic sealing members 40 constrict in the diametrical direction. Accordingly, the leakage of the compressed air (the pressurized fluid) may be avoided, therefore, the force applied to the elastic sealing members 40 so as to press-contact the elastic sealing members 40 against the piston outer circumferential surface B may be increased. As a result, the sealing (the contact) of the elastic sealing members 40 relative to the piston outer circumferential surface B may be enhanced. Hence, the large amount of the electrolyte may be provided between the narrow clearance formed between the piston outer circumferential surface B and the electrode inner circumferential surface 31. As a result, the speed of the surface treatment may be increased.

Sixthly and finally, the partial surface treatment apparatus according to the third embodiment may be modified so that the width of the opening X in the axial direction becomes greater than a width of the wall surface Y of the recessed portion 42 of each elastic sealing member 40 in the axial direction when each elastic sealing member 40 is inserted into the groove portion 71. In this case, the elastic sealing members 40 are more easily compressed so as to reduce (shrink) the inner diameter thereof while the elastic sealing members 40 are pressed against the groove portion 71 by the compressed air. As a result, the sealing (the contact) of the elastic sealing members 40 relative to the piston outer circumferential surface B may be enhanced.

Other Embodiments

The partial surface treatment apparatus according to the first, second and third embodiments may be modified so as to include a pressure applying mechanism for supplying a pressurized fluid such as an operation fluid.

The partial surface treatment apparatus according to the first, second and third embodiments may be modified so that each of the elastic sealing members 40 includes the contact surface, at which each of the elastic sealing members 40 contacts the outer circumferential surface B of the piston A, and a corner portion positioned closer to a circumferential groove of the piston A for guiding a side surface to extend in an oblique direction so as to be orthogonal to the piston outer circumferential surface B of the piston A along the entire circumferential direction of the corresponding elastic sealing member 40.

The partial surface treatment apparatus according to the first, second and third embodiments may be adapted as an electroplating treatment apparatus for executing an electroplating treatment as a surface treatment.

According to the embodiments, the partial surface treatment apparatus includes the first electrode member 15 electrically connected to the piston A, which is made of the metal and which includes the piston ring groove A1 at the piston outer circumferential surface B of the piston A, the second electrode member 17 having the electrode inner circumferential surface 31 facing the piston outer circumferential surface B and the piston ring groove A1 while keeping the distance therefrom, the elastic sealing members 40 made of the nonconductive material, formed in the annular shape and being sealable the clearance formed between the piston outer circumferential surface B and the inner circumferential surface at the portions on the piston outer circumferential surface B above and below the piston ring groove A1, respectively, in the axial direction of the partial surface treatment apparatus, the attachment portions 41 at which the respective elastic sealing members 40 are attached while keeping the distance relative to the piston outer circumferential surface B along the entire circumference thereof, the pressure applying mechanism 51 configured so as to supply the compressed air into the elastic sealing members 40 attached at the respective attachment portions 41 in order to press-contact a radially inner circumferential end portions 44 of the respective elastic sealing members 40 against the piston outer circumferential surface B along the entire circumferences thereof and so as to release the press-contact of the radially inner circumferential end portions 44 of the respective elastic sealing members 40 against the piston outer circumferential surface B and the supply passages 37, through which the electrolyte is supplied to the piston ring groove A1, opening at the electrode inner circumferential surface 31.

Accordingly, a pressure may be applied to the elastic sealing members 40, which are attached at the corresponding attachment portions 41 along the entire circumference thereof while keeping the predetermined distance from the piston outer circumferential surface B of the piston A, by the compressed air supplied to the recessed portions 42 of the respective elastic sealing members 40, so that the elastic sealing members 40 press-fittingly (fluid tightly) contact the piston outer circumferential surface B of the piston A at the entire radially inner circumferential end portions 44. Therefore, even if the piston A is not set radially inwardly of the electrode inner circumferential surface 31 of the second electrode member 17 so as to keep a constant predetermined distance between the piston outer circumferential surface B of the piston A and the electrode inner circumferential surface 31 of the second electrode member 17 along the entire circumferential direction, a pressing force of the elastic sealing members 40 against the piston outer circumferential surface B of the piston A may not fluctuate (vary). Furthermore, even if the pressure of the compressed air (i.e. the pressurized fluid) fluctuates, a press-contact position and a press-contact width of each of the elastic sealing members 40 relative to the piston outer circumferential surface B of the piston A are less likely to fluctuate or be displaced. Accordingly, the electrolyte contact area may be easily set to any desired area. As a result, according to the partial surface treatment apparatus of the embodiments, the sealing of the elastic sealing members 40 relative to the piston outer circumferential surface B of the piston A is less likely to deteriorate, therefore, a treatment efficiency of the surface treatment is less likely to decrease.

According to the embodiments, each of the elastic sealing members 40 includes the recessed portion 42 along the entire circumference thereof so as to open in the radially outward direction thereof.

Accordingly, because the compressed air flows into the recessed portion 42 of each of the elastic sealing members 40 from the opening thereof, the pressure may act on each of the elastic sealing members 40, which are attached on the respective attachment portions 41 in a direction towards the piston outer circumferential surface B of the piston A and in a width direction of the piston ring groove A1. As a result, the posture of each of the elastic sealing members 40, which are attached at the respective attachment portions 41, may be easily stabilized in addition to the enhancement of the sealing (the contact) of the elastic sealing members (40) relative to the piston outer circumferential surface B of the piston A.

According to the embodiments, the radially outer circumferential edge portions 81 and radially inner circumferential edge portions 82 of each of the elastic sealing members 40 are displaced towards the center thereof in the radial direction thereof in response to the supply of pressurized fluid (the compressed air) thereto so that the inner diameter of each of the elastic sealing members 40 is decreased.

Accordingly, because the elastic sealing members 40 expand towards the piston A, which is arranged radially inwardly of the second electrode member 17, so that the inner diameter thereof decreases, the elastic sealing members 40 itself slidably move towards the piston A. Therefore, the sealing (the contact) of the elastic sealing members 40 relative to the piston A may be enhanced while avoiding a positional displacement of the elastic sealing members 40. Furthermore, because the entire elastic sealing members 40 expand towards the piston A so that the inner diameter thereof decreases, a tension applied to the elastic sealing members 40 while expanding towards the piston A and returning to the initial shape is avoided from being concentrated on one point. As a result, because deterioration of the elastic sealing members 40 is reduced, a number of repeated use of the elastic sealing members 40 may be increased.

According to the embodiments, each of the elastic sealing members 40 includes the contact surface Z, at which each of the elastic sealing members 40 is contactable with the piston outer circumferential surface B, and the contact surface Z of each of the elastic sealing members 40 is formed as a surface parallel to the axial direction of the elastic sealing member 40.

Accordingly, a close-contact area between the elastic sealing members 40 and the piston A may be increased, so that the sealing (the contact) therebetween may be enhanced. Accordingly, the large amount of the electrolyte may be provided between the clearance, which is formed between the electrode inner circumferential surface 31 of the second electrode member 17 and the piston A and which is sealed by the elastic sealing members 40. Furthermore, an area to which the surface treatment is applied may be set to any desired area by adjusting an area of a surface of each of the elastic sealing members 40 extending in parallel to the axial direction. For example, the area to which the surface treatment is applied may be reduced.

According to the embodiments, each of the elastic sealing members 40 is configured so as to be insertable into the groove portion 71 formed by the attachment portion 41 and the second electrode member 17. Each of the elastic sealing members 40 is formed so that a width in the axial direction between the radially outer circumferential edge portions 81 of the elastic sealing member 40 before being inserted into the groove portion 71 is greater than the opening width 71 a of the groove portion 71, and the width in the axial direction between the radially inner circumferential edge portions 82 of each of the elastic sealing members 40 before being inserted into the groove portion 71 is narrower than the opening width 71 a of the groove portion 71.

Accordingly, when the elastic sealing members 40 are fitted into the groove portion 71, a biasing force acts on the elastic sealing members 40. Therefore, the sealing (the contact) of the elastic sealing members 40 relative to the piston A (EP: the treatment object) may be enhanced by the biasing force.

According to the modified example of the third embodiment, each of the elastic sealing members 40 is formed so as to be protrudable in the radially inward direction relative to the grove portion 71, which is formed in the annular shape and which is defined by the corresponding attachment portion 41 and the second electrode member 17 so as to include the opening X opening in the radially inward direction.

Accordingly, the clearance formed between the piston outer circumferential surface B and the electrode inner circumferential surface 31 may be narrowed. As a result, a large amount of the electrolyte may be provided into the narrow clearance formed between the piston outer circumferential surface B and the electrode inner circumferential surface 31, which may further result in increasing the speed of surface treatment (shortening the time necessary for the surface treatment).

According to another modified example of the third embodiment, each of the elastic sealing members 40 includes the side wall portions 43 defining the recessed portion 42. The thickness of each of the side wall portions 43 is formed to be thinner than the width of the recessed portion 42 in the axial direction of the elastic sealing member 40.

Accordingly, the side wall portions 43 of each of the elastic sealing members 40 become more easily deformable, therefore, the side wall portions 43 of each of the elastic sealing members 40 are more easily press-contact a wall surface of the groove portion 71 by the compressed air (the pressurized fluid). As a result, the sealing (the contact) of the elastic sealing members 40 against the wall surface of the groove portion 71 may be increased. Furthermore, in a case where a pressure applied to the elastic sealing members 40 is eased (removed), each of the elastic sealing members 40 is enlarged in the diametrical direction in the radially outward direction while a pressing force of the wall portions 43 is eased. Therefore, a force applied to the elastic sealing members 40 while being enlarged in the diametrical direction may be eased. Accordingly, durability of the elastic sealing members 40 may be enhanced.

According to a further example of the third embodiment, each of the elastic sealing members 40 further includes the recessed portion 42, which includes the wall surface Y so as to be positioned closer to the radially inner circumferential edge portions 82 of the elastic sealing member 40 relative to the intermediate point between the radially outer circumferential edge portions 81 and the radially inner circumferential edge portions 82 of the elastic sealing member 40.

Accordingly, each of the elastic sealing members 40 may be easily elastically deformable in an inner diameter reducing direction, so that the elastic sealing members 40 may more easily press-fittingly contact the piston outer circumferential surface B. As a result, the sealing (the contact) of the elastic sealing members 40 relative to the piston outer circumferential surface B may be enhanced.

According to a further modified example of the third embodiment, each of the elastic sealing members 40 further includes the recessed portion 42, which includes the wall surface Y so as to be positioned closer to the radially inner circumferential edge portions 82 of the elastic sealing member 40. The wall surface Y is formed as a surface parallel to the axial direction of the elastic sealing member 40 along the contact surface Z of the elastic sealing member 40 at which the elastic sealing member 40 is contactable with the piston outer circumferential surface B of the piston A.

Accordingly, the wall surface Y serving as the bottom portion of the recessed portion 43 is formed as a surface parallel to the contact surface Z of the corresponding elastic sealing member 40 at which the elastic sealing member 40 contacts the outer circumferential surface B of the piston A. Therefore, the contact surface Z of each of the elastic sealing members 40 may evenly pressed against the piston outer circumferential surface B by the compressed air (the pressurized fluid). As a result, the sealing (the contact) of the elastic sealing members 40 against the piston outer circumferential surface B may be enhanced.

According to a further modified example of the third embodiment, each of the elastic sealing members 40 is slidably displaced in the radially inward direction while pressing the wall surface of the groove portion 71 while each of the elastic sealing members 40 is displaced so that the inner diameter thereof decreases.

Accordingly, the leakage of the compressed air (the pressurized fluid) may be avoided, therefore, the force applied to the elastic sealing members 40 so as to press-contact the elastic sealing members 40 against the piston outer circumferential surface B may be increased. As a result, the sealing (the contact) of the elastic sealing members 40 relative to the piston outer circumferential surface B may be enhanced. Hence, the large amount of the electrolyte may be provided between the narrow clearance formed between the piston outer circumferential surface B and the electrode inner circumferential surface 31. As a result, the speed of the surface treatment may be increased.

According to a further modified example of the third embodiment, each of the elastic sealing members 40 further includes the recessed portion 42 and is formed so that the width of the wall surface of the recessed portion in the axial direction becomes greater than the width of the opening X in the axial direction while the elastic sealing member 40 is inserted into the groove potion formed between the corresponding attachment portion 41 and the second electrode member 17.

Accordingly, in this case, the elastic sealing members 40 are more easily compressed so as to reduce (shrink) the inner diameter thereof while the elastic sealing members 40 are pressed against the groove portion 71 by the compressed air. As a result, the sealing (the contact) of the elastic sealing members 40 relative to the piston outer circumferential surface B may be enhanced.

According to the embodiments, each of the elastic sealing members 40 includes the contact surface 57, at which the elastic sealing member 40 is contactable with the piston outer circumferential surface B, and the corner portions 59, which are positioned so as to be closer to the piston ring groove A1 and which guide the respective side surfaces 58 to extend in the direction orthogonal to the piston outer circumferential surface B, so as to extend along the entire circumference of the elastic sealing member 40 in the annular shape.

Accordingly, the border of the electrolyte contact area may be set along the corner portions 59, which are formed in the annular shape along the respective elastic sealing members 40. Accordingly, the electrolyte contact area may be easily set to any desired area.

According to the embodiments, a partial surface treatment apparatus, includes the first electrode member 15 electrically connected to the piston A, which is made of the metal and which includes the piston ring groove A at the piston outer circumferential surface B of the piston A, the second electrode member 17 having the electrode inner circumferential surface 31 facing the piston outer circumferential surface B and the piston ring groove A1 while keeping the distance therefrom, the elastic sealing members 40 made of the nonconductive material, formed in the annular shape, being sealable the clearance formed between the piston outer circumferential surface B and the inner circumferential surface at portions on the piston outer circumferential surface B above and below the piston ring groove A1 in an axial direction of the partial surface treatment apparatus, and including a recessed portion along an entire circumference thereof so as to open in a radially outward direction thereof and a displacement restricting portion so as to extend along an entire opening portion in a circumferential direction thereof in order to prevent a radially outer circumferential portion of the elastic sealing member defining the opening portion from being displaced towards the piston outer circumferential surface B, the attachment portions 41 at which the respective elastic sealing members 40 are attached while keeping the distance relative to the piston outer circumferential surface B along the entire circumference thereof, the pressure applying mechanism 51 configured so as to supply the pressurized fluid (the compressed air) into the elastic sealing members 40 attached at the respective attachment portions 41 in order to press-contact the radially inner circumferential end portions 44 of the respective elastic sealing members 40 against the piston outer circumferential surface B along the entire circumference thereof and so as to release the press-contact of the radially inner circumferential end portions 44 of the respective elastic sealing members 40 against the piston outer circumferential surface B, and the supply passages 37, through which the electrolyte is supplied to the piston ring groove A1, opening at the electrode inner circumferential surface 31.

The compressed air supplied to the elastic sealing members 40 flows into the recessed portions 42 thereof, whose opening portions are restricted from being displayed towards the piston outer circumferential surface B of the piston A. Accordingly, a radially inner circumferential portion of the recessed portion 42 of each of the elastic sealing members 40 relative to the corresponding opening portion may be elastically deformed towards the piston outer circumferential surface B of the piston A, so that each of the elastic sealing member 40 press-fittingly contacts the piston outer circumferential surface B of the piston A. More specifically, the radially inner circumferential portion of the recessed portion 42 of each of the elastic sealing members 40 may be evenly and elastically deformed towards the piston outer circumferential surface B of the piston A. Therefore, in the case where the piston A is not set radially inwardly of the second electrode member 17 so as to be equally distanced therefrom along the entire circumference of the second electrode member 17, the piston A is pressed by the elastic sealing members 40, which are elastically reformed so as to contact the piston A, so that a position of the piston A is corrected to a position at which the piston A is positioned radially inwardly of the second electrode member 17 so as to be equally distanced therefrom. Accordingly, a flow condition of the electrolyte between the piston A and the second electrode member 17 may be set to be constant along the entire circumference of the second electrode member 17, so that the surface treatment is evenly applied to the entire circumference of the piston A. Furthermore, after the surface treatment is completed, the radially inner circumferential end portion 44 of each of the elastic sealing members 40, which is positioned radially inwardly of the opening portion, is elastically deformed towards the displacement restricting portion 45 so as to return to the initial position, so that another piston A is easily set so as not to contact the elastic sealing members 40 for the next surface treatment.

According to the embodiments, the partial surface treatment apparatus, includes the first electrode member 15 electrically connected to the piston A, which is made of the metal and which includes the piston ring groove A1 at the piston outer circumferential surface B of the piston A, the second electrode member 17 having the electrode inner circumferential surface 31 facing the piston outer circumferential surface B and the piston ring groove A1 while keeping the distance therefrom, the elastic sealing members 40 made of the nonconductive material, formed in the annular shape, being sealable the clearance formed between the piston outer circumferential surface B and the inner circumferential surface at portions on the piston outer circumferential surface B above and below the piston ring groove A1 in the axial direction of the partial surface treatment apparatus and including the contact surfaces 57, at which the elastic sealing members 40 are contactable with the piston outer circumferential surface B, and the corner portions 59, which is positioned so as to be closer to the piston ring groove A1 and which guide the respective side surfaces 58 to extend in the direction orthogonal to the piston outer circumferential surface B, so as to extend along the entire circumference of the corresponding elastic sealing members 40 in the annular shape, the attachment portions 41 at which the respective elastic sealing members 40 are attached while keeping the distance relative to the piston outer circumferential surface B along the entire circumference thereof, the pressure applying mechanism 51 configured so as to supply a pressurized fluid into the elastic sealing members 40 attached at the respective attachment portions 41 in order to press-contact the radially inner circumferential end portions 44 of the respective elastic sealing members 40 against the piston outer circumferential surface B along the entire circumference thereof and so as to release the press-contact of the radially inner circumferential end portions 44 of the respective elastic sealing members 40 against the piston outer circumferential surface B, and the supply passages 37, through which the electrolyte is supplied to the piston ring groove A1, opening at the electrode inner circumferential surface 31.

Accordingly, a pressure may be applied to the elastic sealing members 40, which are attached at the corresponding attachment portions 41 along the entire circumference thereof while keeping the predetermined distance from the piston outer circumferential surface B of the piston A, by the compressed air supplied to the recessed portions 42 of the respective elastic sealing members 40, so that the elastic sealing members 40 press-fittingly (fluid tightly) contact the piston outer circumferential surface B of the piston A at the entire radially inner circumferential end portions 44. Therefore, even if the piston A is not set radially inwardly of the electrode inner circumferential surface 31 of the second electrode member 17 so as to keep a constant predetermined distance between the piston outer circumferential surface B of the piston A and the electrode inner circumferential surface 31 of the second electrode member 17 along the entire circumferential direction, a pressing force of the elastic sealing members 40 against the piston outer circumferential surface B of the piston A may not fluctuate (vary). Furthermore, even if the pressure of the compressed air (i.e. the pressurized fluid) fluctuates, a press-contact position and a press-contact width of each of the elastic sealing members 40 relative to the piston outer circumferential surface B of the piston A are less likely to fluctuate or be displaced. Accordingly, the electrolyte contact area may be easily set to any desired area. As a result, according to the partial surface treatment apparatus of the embodiments, the sealing of the elastic sealing members 40 relative to the piston outer circumferential surface B of the piston A is less likely to deteriorate, therefore, a treatment efficiency of the surface treatment is less likely to decrease. Furthermore, accordingly, the border of the electrolyte contact area may be set along the corner portions 59, which are formed in the annular shape along the respective elastic sealing members 40. As a result, the electrolyte contact area may be easily set to any desired area.

The principles, preferred embodiment and mode of operation of the present invention have been described in the foregoing specification. However, the invention which is intended to be protected is not to be construed as limited to the particular embodiments disclosed. Further, the embodiments described herein are to be regarded as illustrative rather than restrictive. Variations and changes may be made by others, and equivalents employed, without departing from the spirit of the present invention. Accordingly, it is expressly intended that all such variations, changes and equivalents which fall within the spirit and scope of the present invention as defined in the claims, be embraced thereby. 

1. A partial surface treatment apparatus, comprising: a first electrode member electrically connected to a treatment object, which is made of a metal and which includes a circumferential groove at an outer circumferential surface of the treatment object; a second electrode member having an annular-shaped inner circumferential surface facing the outer circumferential surface and the circumferential groove while keeping a distance therefrom; an elastic sealing member made of a nonconductive material, formed in an annular shape and being sealable a clearance formed between the outer circumferential surface and the inner circumferential surface at portions on the outer circumferential surface above and below the circumferential groove in an axial direction of the partial surface treatment apparatus; an attachment portion at which the elastic sealing member is attached while keeping the distance relative to the outer circumferential surface along an entire circumference thereof; a pressure applying mechanism configured so as to supply a pressurized fluid into the elastic sealing member attached at the attachment portion in order to press-contact a radially inner circumferential end portion of the elastic sealing member against the outer circumferential surface along the entire circumference thereof and so as to release a press-contact of the radally inner circumferential end portion of the elastic sealing member against the outer circumferential surface; and a supply passage, through which an electrolyte is supplied to the circumferential groove, opening at the inner circumferential surface.
 2. The partial surface treatment apparatus according to claim 1, wherein the elastic sealing member includes a recessed portion along an entire circumference thereof so as to open in a radially outward direction thereof.
 3. The partial surface treatment apparatus according to claim 2, wherein radially outer circumferential edge portions and radially inner circumferential edge portions of the elastic sealing member are displaced towards a center of the elastic sealing member in a radial direction thereof in response to the supply of pressurized fluid thereto so that an inner diameter of the elastic sealing member is decreased.
 4. The partial surface treatment apparatus according to claim 3, wherein the elastic sealing member includes a contact surface, at which the elastic sealing member is contactable with the outer circumferential surface, and the contact surface of the elastic sealing member is formed as a surface parallel to an axial direction of the elastic sealing member.
 5. The partial surface treatment apparatus according to claim 3, wherein the elastic sealing member is configured so as to be insertable into a groove portion formed by the attachment portion and the second electrode member, the elastic sealing member is formed so that a width in the axial direction between radially outer circumferential edge portions of the elastic sealing member before being inserted into the groove portion is greater than an opening width of the groove portion, and a width in the axial direction between radially inner circumferential edge portions of the elastic sealing member before being inserted into the groove portion is narrower than the opening width of the groove portion.
 6. The partial surface treatment apparatus according to claim 3, wherein the elastic sealing member is formed so as to be protrudable in a radially inward direction relative to a grove portion, which is formed in an annular shape and which is defined by the attachment portion and the second electrode member so as to include an opening, which opens in the radially inward direction.
 7. The partial surface treatment apparatus according to claim 3, wherein the elastic sealing member includes side wall portions defining a recessed portion, a thickness of each of the side wall portions is formed to be thinner than a width of the recessed portion in an axial direction of the elastic sealing member.
 8. The partial surface treatment apparatus according to claim 3, wherein the elastic sealing member further includes a recessed portion, which includes a wall portion so as to be positioned closer to radially inner circumferential edge portions of the elastic sealing member relative to an intermediate point between radially outer circumferential edge portions and the radially inner circumferential edge portions of the elastic sealing member.
 9. The partial surface treatment apparatus according to claim 3, wherein the elastic sealing member further includes a recessed portion, which includes a wall portion so as to be positioned closer to radially inner circumferential edge portions of the elastic sealing member, and the wall portion is formed as a surface parallel to an axial direction of the elastic sealing member along a contact surface of the elastic sealing member at which the elastic sealing member is contactable with the outer circumferential surface of the treatment object.
 10. The partial surface treatment apparatus according to claim 3, wherein the elastic sealing member is slidably displaced in a radially inward direction while pressing a wall surface of a groove portion while the elastic sealing member is displaced so that the inner diameter thereof decreases.
 11. The partial surface treatment apparatus according to claim 3, wherein the elastic sealing member further includes a recessed portion, and the elastic sealing member is formed so that a width of a wall portion of the recessed portion in an axial direction becomes greater than a width of an opening in the axial direction while the elastic sealing member is inserted into a groove potion formed between the attachment portion and the second electrode member.
 12. The partial surface treatment apparatus according to claim 3, wherein the elastic sealing member includes a contact surface, at which the elastic sealing member is contactable with the outer circumferential surface, and a corner portion, which is positioned so as to be closer to the circumferential groove and which guides a side surface to extend in a direction orthogonal to the outer circumferential surface, so as to extend along the entire circumference of the elastic sealing member in an annular shape.
 13. A partial surface treatment apparatus, comprising: a first electrode member electrically connected to a treatment object, which is made of a metal and which includes a circumferential groove at an outer circumferential surface of the treatment object; a second electrode member having an annular-shaped inner circumferential surface facing the outer circumferential surface and the circumferential groove while keeping a distance therefrom; an elastic sealing member made of a nonconductive material, formed in an annular shape, being sealable a clearance formed between the outer circumferential surface and the inner circumferential surface at portions on the outer circumferential surface above and below the circumferential groove in an axial direction of the partial surface treatment apparatus, and including a recessed portion along an entire circumference thereof so as to open in a radially outward direction thereof and a displacement restricting portion so as to extend along an entire opening portion in a circumferential direction thereof in order to prevent a radially outer circumferential portion of the elastic sealing member defining the opening portion from being displaced towards the outer circumferential surface; an attachment portion at which the elastic sealing member is attached while keeping the distance relative to the outer circumferential surface along an entire circumference thereof; a pressure applying mechanism configured so as to supply a pressurized fluid into the elastic sealing member attached at the attachment portion in order to press-contact a radially inner circumferential end portion of the elastic sealing member against the outer circumferential surface along the entire circumference thereof and so as to release a press-contact of the radially inner circumferential end portion of the elastic sealing member against the outer circumferential surface; and a supply passage, through which an electrolyte is supplied to the circumferential groove, opening at the inner circumferential surface.
 14. A partial surface treatment apparatus, comprising: a first electrode member electrically connected to a treatment object, which is made of a metal and which includes a circumferential groove at an outer circumferential surface of the treatment object; a second electrode member having an annular-shaped inner circumferential surface facing the outer circumferential surface and the circumferential groove while keeping a distance therefrom; an elastic sealing member made of a nonconductive material, formed in an annular shape, being sealable a clearance formed between the outer circumferential surface and the inner circumferential surface at portions on the outer circumferential surface above and below the circumferential groove in an axial direction of the partial surface treatment apparatus and including a contact surface, at which the elastic sealing member is contactable with the outer circumferential surface, and a corner portion, which is positioned so as to be closer to the circumferential groove and which guides a side surface to extend in a direction orthogonal to the outer circumferential surface, so as to extend along the entire circumference of the elastic sealing member in an annular shape; an attachment portion at which the elastic sealing member is attached while keeping the distance relative to the outer circumferential surface along an entire circumference thereof; a pressure applying mechanism configured so as to supply a pressurized fluid into the elastic sealing member attached at the attachment portion in order to press-contact a radially inner circumferential end portion of the elastic sealing member against the outer circumferential surface along the entire circumference thereof and so as to release a press-contact of the radially inner circumferential end portion of the elastic sealing member against the outer circumferential surface; and a supply passage, through which an electrolyte is supplied to the circumferential groove, opening at the inner circumferential surface. 